Add a systemd unit file

It's just better if we get activated via systemd rather than dbus.
Various bits of configury/makefile taken from polkit.

https://bugs.freedesktop.org/show_bug.cgi?id=58468

data/Makefile.am

@@ -9,6 +9,15 @@ $(dbus_services_DATA): $(dbus_services_in_files)
 dbus_confdir = $(sysconfdir)/dbus-1/system.d
 dbus_conf_DATA = net.reactivated.Fprint.conf
 
+systemdservice_in_files = fprintd.service.in
+
+if HAVE_SYSTEMD
+systemdservicedir       = $(systemdsystemunitdir)
+systemdservice_DATA     = $(systemdservice_in_files:.service.in=.service)
+$(systemdservice_DATA): $(systemdservice_in_files) Makefile
+	@sed -e "s|\@libexecdir\@|$(libexecdir)|" $< > $@
+endif
+
 polkitdir = $(datadir)/polkit-1/actions
 polkit_in_files = net.reactivated.fprint.device.policy.in
 

data/fprintd.service.in

@@ -0,0 +1,8 @@
+[Unit]
+Description=Fingerprint Authentication Daemon
+Documentation=man:fprintd(1)
+
+[Service]
+Type=dbus
+BusName=net.reactivated.Fprint
+ExecStart=@libexecdir@/fprintd

data/net.reactivated.Fprint.service.in

@@ -2,3 +2,4 @@
 Name=net.reactivated.Fprint
 Exec=@LIBEXECDIR@/fprintd
 User=root
+SystemdService=fprintd.service